Field of the Invention
This invention relates to extrusion systems as used to form sheets/sheet products using a supply of flowable material.
Background Art
One basic extrusion sheet forming system utilizes the combination of a barrel assembly, a polymer filter assembly, and a die assembly through which flowable material is delivered from a supply to a processing/roll assembly through which one or more sheet layers are formed. An exemplary system is shown in U.S. Pat. No. 8,021,140. Flowable material from the supply is delivered through the barrel assembly to the polymer filter assembly, within which filtering of the flowable material takes place. From the polymer filter assembly, the filtered, flowable material is directed to the die assembly which causes a controlled, precise delivery of the flowable material to a processing/roll system upon which the flowable material is solidified and formed into a sheet layer. The sheet layer may be accumulated by itself or united with one or more additional sheet layers to produce a completed product or an intermediate product that is further processed downstream, or elsewhere.
Polymer materials utilized in these systems are commonly heated to elevated temperatures that cause expansion of metal parts that must be accommodated to avoid deformation and skewing of system assemblies/components that could compromise the integrity of the sheets and products generated. Various modifications have been made to such systems in the past to minimize deformation and accommodate expansion and contraction of interacting metal parts.
For example, it is known to support the die assembly on a wheeled cart or using a metal-to-metal slide that permits a modicum of lengthwise shifting. These arrangements allow out-of-plane loads to be transmitted between components upstream and downstream of the die assembly. These systems lack the ability to maintain precise component alignment and do not support the weight of the die assembly when a misalignment naturally occurs.
The industry continues to seek designs that better accommodate thermal expansion and contraction in an efficient and practical manner.